Diodes & transistors worksheet with answers

Free printable Diodes & transistors worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
+−Vs​5 VR = 3.3 kΩD​I = ?

A 5 V DC source drives current through a 3.3 kΩ resistor in series with a forward-biased silicon diode. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

Vs = 5 VR = 3.3 kΩVD = 0.7 V
I = mA
2.Easy
+−9 V100 Ω6.2 VIR​ = ?

A 6.2 V Zener diode is fed from 9 V through a 100 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 9 VVZ = 6.2 VR = 100 Ω
IR = mA
3.Medium
+−12 VR = ?4 × 2.2 V20 mA

4 green LEDs (forward voltage 2.2 V each) are connected in series with a resistor to a 12 V supply. Find the resistance R that sets the current to 20 mA.

Vs = 12 VVF = 2.2 Vn = 4I = 20 mA
R = Ω
4.Medium
RC​ = 1 kΩβ = 50VCC​ = 12 VRB​ = 390 kΩ

An NPN transistor with β = 50 is biased by a base resistor RB = 390 kΩ from the supply VCC = 12 V. The collector resistor is RC = 1 kΩ and the emitter is grounded. Take VBE = 0.7 V and assume the transistor is in the active region. Find the collector–emitter voltage VCE.

VCC = 12 VRB = 390 kΩRC = 1 kΩβ = 50VBE = 0.7 V
VCE = V
5.Hard
RC​ = 100 Ωβ = 100VCC​ = 5 V5 VRB​ = ?

An NPN transistor with β = 100 switches a 100 Ω load resistor connected between VCC = 5 V and its collector. The emitter is grounded. The base is driven from a 5 V logic output through a base resistor RB. Take VBE = 0.7 V and VCE(sat) = 0.2 V. For reliable switching, design for a base current 4 times the minimum needed for saturation. Find RB in kΩ.

VCC = 5 VRC = 100 Ωβ = 100Vin = 5 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 4
RB = kΩ
6.Hard
RC​ = 150 Ωβ = 80VCC​ = 12 V3.3 VRB​ = ?

An NPN transistor with β = 80 switches a 150 Ω load resistor connected between VCC = 12 V and its collector. The emitter is grounded. The base is driven from a 3.3 V logic output through a base resistor RB. Take VBE = 0.7 V and VCE(sat) = 0.2 V. For reliable switching, design for a base current 2 times the minimum needed for saturation. Find RB in kΩ.

VCC = 12 VRC = 150 Ωβ = 80Vin = 3.3 VVBE = 0.7 VVCE(sat) = 0.2 Voverdrive = 2
RB = kΩ

Answer key

  1. 1. I = 1.303 mA
  2. 2. IR = 28 mA
  3. 3. R = 160 Ω
  4. 4. VCE = 10.55 V
  5. 5. RB = 2.24 kΩ
  6. 6. RB = 1.322 kΩ

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